US8487968B2 - Display device and contrast enhancement method thereof - Google Patents

Display device and contrast enhancement method thereof Download PDF

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US8487968B2
US8487968B2 US12/944,323 US94432310A US8487968B2 US 8487968 B2 US8487968 B2 US 8487968B2 US 94432310 A US94432310 A US 94432310A US 8487968 B2 US8487968 B2 US 8487968B2
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luminance
apl
digital video
pixel
video data
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US20110317074A1 (en
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Suhyung Kim
Seonggyun KIM
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LG Display Co Ltd
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2092—Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G5/00—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators
    • G09G5/02—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the way in which colour is displayed
    • G09G5/04—Control arrangements or circuits for visual indicators common to cathode-ray tube indicators and other visual indicators characterised by the way in which colour is displayed using circuits for interfacing with colour displays
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0233—Improving the luminance or brightness uniformity across the screen
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/066—Adjustment of display parameters for control of contrast
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0673—Adjustment of display parameters for control of gamma adjustment, e.g. selecting another gamma curve
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2360/00—Aspects of the architecture of display systems
    • G09G2360/16—Calculation or use of calculated indices related to luminance levels in display data
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2370/00—Aspects of data communication
    • G09G2370/04—Exchange of auxiliary data, i.e. other than image data, between monitor and graphics controller
    • G09G2370/045—Exchange of auxiliary data, i.e. other than image data, between monitor and graphics controller using multiple communication channels, e.g. parallel and serial
    • G09G2370/047—Exchange of auxiliary data, i.e. other than image data, between monitor and graphics controller using multiple communication channels, e.g. parallel and serial using display data channel standard [DDC] communication
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
    • G09G3/3611—Control of matrices with row and column drivers
    • G09G3/3648—Control of matrices with row and column drivers using an active matrix

Definitions

  • Exemplary embodiments of the disclosure relate to a display device and a contrast enhancement method thereof.
  • Examples of a display device include a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an organic light emitting diode (OLED) display. Most of them have been put to practical use in electric home appliances or personal digital appliances, etc. and have been marketed.
  • LCD liquid crystal display
  • FED field emission display
  • PDP plasma display panel
  • OLED organic light emitting diode
  • U.S. Pat. No. 7,102,697 discloses an example of a method capable of improving the contrast characteristic. More specifically, U.S. Pat. No. 7,102,697 discloses a typical global contrast enhancement method. In U.S. Pat. No. 7,102,697, a luminance transfer curve is generated through a histogram analysis of a previous frame, and digital video data of a current frame is mapped to the luminance transfer curve, thereby performing a contrast enhancement of an image.
  • Exemplary embodiments of the disclosure provide a display device and a contrast enhancement method thereof capable of minimizing a detailed loss of an image and improving contrast characteristics.
  • a display device comprising a display panel on which data lines and gate lines are positioned, a data driving circuit configured to drive the data lines, a scan driving circuit configured to drive the gate lines, a timing controller configured to control the data driving circuit and the scan driving circuit, and a data modulation circuit including a local modulation circuit and a global modulation circuit, the local modulation circuit being configured to map luminance components of input digital video data to a luminance transfer curve selected or generated for each pixel based on an average picture level (APL) of each pixel and perform a first modulation on the luminance components of the input digital video data so as to expand a gray level distribution of a specific portion of an input image, the global modulation circuit being configured to perform a second modulation on first modulated luminance components of the input digital video data so as to improve an entire contrast characteristic of the input image and supply second modulated luminance components of the input digital video data to the timing controller.
  • APL average picture level
  • a contrast enhancement method of a display device including a display panel on which data lines and gate lines are positioned, a data driving circuit for driving the data lines, a scan driving circuit for driving the gate lines, a timing controller for controlling the data driving circuit and the scan driving circuit, the contrast enhancement method comprising mapping luminance components of input digital video data to a luminance transfer curve selected or generated for each pixel based on an average picture level (APL) of each pixel and performing a first modulation on the luminance components of the input digital video data so as to expand a gray level distribution of a specific portion of an input image, and performing a second modulation on first modulated luminance components of the input digital video data so as to improve an entire contrast characteristic of the input image and supplying second modulated luminance components of the input digital video data to the timing controller.
  • APL average picture level
  • FIG. 1 illustrates a display device according to an exemplary embodiment of the invention
  • FIG. 2 illustrates an exemplary configuration of a data modulation circuit
  • FIG. 3 illustrates a plurality of virtual blocks obtained by dividing a display screen of a display device in a matrix form
  • FIG. 4A illustrates an input image
  • FIG. 4B illustrates an image based on a calculated average picture level (APL) of each block
  • FIG. 4C illustrates an image based on an interpolated APL of each block
  • FIG. 4D illustrates exemplary luminance transfer curves based on an APL of each block
  • FIG. 4E illustrates an exemplary luminance transfer curve corresponding to an APL of each pixel
  • FIG. 4F illustrates an image on which a local contrast enhancement is performed
  • FIG. 5 illustrates a detailed enhancement effect when both a local contrast and a global contrast are enhanced, compared with a detailed enhancement effect when only a global contrast is enhanced in the related art
  • FIG. 6 illustrates an exemplary image in which a halo is generated
  • FIG. 7 illustrates another exemplary configuration of a data modulation circuit
  • FIG. 8 illustrates a low pass filter
  • FIG. 9 illustrates an APL of each block before and after a low pass filter is applied.
  • FIG. 1 illustrates a display device according to an exemplary embodiment of the invention.
  • the display device may be implemented as a flat panel display device such as a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an organic light emitting diode (OLED) display.
  • LCD liquid crystal display
  • FED field emission display
  • PDP plasma display panel
  • OLED organic light emitting diode
  • the liquid crystal display is taken as an example of the display device.
  • the display device includes a display panel 10 , a data modulation circuit 11 , a timing controller 12 , a data driving circuit 13 , and a scan driving circuit 14 .
  • the display panel 10 includes an upper glass substrate, a lower glass substrate, and a liquid crystal layer formed between the upper and lower glass substrates.
  • a plurality of data lines DL and a plurality of gate lines GL are positioned to cross one another on the lower glass substrate of the display panel 10 .
  • a plurality of liquid crystal cells Clc are arranged on the display panel 10 in a matrix form based on a crossing structure of the data lines DL and the gate lines GL.
  • Each of the liquid crystal cells Clc includes a thin film transistor (TFT), a pixel electrode 1 connected to the TFT, a common electrode 2 opposite the pixel electrode 1 , a storage capacitor Cst, and the like. Black matrixes, color filters, etc. are formed on the upper glass substrate of the display panel 10 .
  • the common electrode 2 In a vertical electric field driving manner such as a twisted nematic (TN) mode and a vertical alignment (VA) mode, the common electrode 2 is formed on the upper glass substrate. In a horizontal electric field driving manner such as an in-plane switching (IPS) mode and a fringe field switching (FFS) mode, the common electrode 2 is formed on the lower glass substrate along with the pixel electrode 1 .
  • the liquid crystal cells Clc include R liquid crystal cells for red display, G liquid crystal cells for green display, and B liquid crystal cells for blue display.
  • the R liquid crystal cell, the G liquid crystal cell, and the B liquid crystal cell constitute a unit pixel.
  • Polarizing plates are respectively attached to the upper and lower glass substrates of the display panel 10 . Alignment layers for setting a pre-tilt angle of liquid crystals are respectively formed on the inner surfaces contacting the liquid crystals in the upper and lower glass substrates of the display panel 10 .
  • the data modulation circuit 11 performs both a global contrast enhancement and a local contrast enhancement, thereby minimizing a detailed loss of an image and improving contrast characteristic.
  • the data modulation circuit 11 performs the local contrast enhancement prior to the global contrast enhancement.
  • the data modulation circuit 11 previously expands a gray level distribution of a detailed portion of the image (for example, a very dark portion or a very bright portion of the image) through the local contrast enhancement, thereby minimizing the detailed loss of the image to be generated in the global contrast enhancement.
  • the data modulation circuit 11 sequentially modulates luminance components of digital video data RGB received from a system board (not shown) in conformity with the improvement of the local and global contrast characteristics and then supplies the modulated digital video data R′G′B′ to the timing controller 12 . Further, the data modulation circuit 11 supplies timing signals Vsync, Hsync, DE, and DCLK received from the system board to the timing controller 12 .
  • the data modulation circuit 11 is described in detail below with reference to FIGS. 2 to 9
  • the timing controller 12 arranges the modulated digital video data R′G′B′ received from the data modulation circuit 11 in conformity with a resolution of the display panel 10 and supplies the modulated digital video data R′G′B′ to the data driving circuit 13 .
  • the timing controller 12 generates a data control signal DDC for controlling operation timing of the data driving circuit 13 and a scan control signal GDC for controlling operation timing of the scan driving circuit 14 based on the timing signals Vsync, Hsync, DE, and DCLK received from the data modulation circuit 11 .
  • the data control signal DDC includes a source start pulse SSP, a source sampling clock SSC, a polarity control signal POL, a source output enable SOE, and the like.
  • the scan control signal GDC includes a gate start pulse GSP, a gate shift clock GSC, a gate output enable GOE, and the like.
  • the data driving circuit 13 includes a plurality of source driver integrated circuits (ICs).
  • the data driving circuit 13 latches the modulated digital video data R′G′B′ received from the timing controller 12 in response to the data control signal DDC and converts the modulated digital video data R′G′B′ into positive and negative analog gamma compensation voltages.
  • the data driving circuit 13 then supplies the positive and negative analog gamma compensation voltages to the data lines DL.
  • the scan driving circuit 14 generates a scan pulse (or a gate pulse) in response to the scan control signal GDC and then sequentially supplies the scan pulse to the gate lines GL.
  • the display device may be implemented as a reflective display device or a backlit display device.
  • the backlit display device may further include a backlight unit for providing light to the display panel 10 .
  • the backlight unit may be implemented as an edge type backlight unit, in which light sources are positioned opposite the side of a light guide plate, or a direct type backlight unit, in which light sources are positioned under a diffusion plate.
  • FIG. 2 illustrates an exemplary configuration of the data modulation circuit 11 .
  • the data modulation circuit 11 includes a local modulation circuit 111 for local contrast enhancement and a global modulation circuit 112 for global contrast enhancement.
  • the local modulation circuit 111 includes a representative value calculating unit 111 A, a representative value interpolating unit 111 B, a luminance transfer curve generating unit 111 C, and a data modulating unit 111 D.
  • the representative value calculating unit 111 A receives luminance components Y of the input digital video data RGB (for example, luminance components shown in FIG. 4A ) from a luminance/color difference component separating unit (not shown) included in the data modulation circuit 11 .
  • the representative value calculating unit 111 A matches the luminance components Y of the input digital video data RGB to a plurality of virtual blocks B (0, 0) to B (n ⁇ 1, m ⁇ 1) obtained by dividing a display screen of the display panel 10 in a matrix form as shown in FIG. 3 to calculate a representative value of each of the virtual blocks B (0, 0) to B (n ⁇ 1, m ⁇ 1).
  • the representative value of each block may be implemented by an average picture level (APL) of each block.
  • APL average picture level
  • the representative value calculating unit 111 A obtains a maximum gray level of each pixel in each block and divides a sum of the maximum gray levels of the pixels included in each block by the total number of pixels of each block, so as to calculate an APL APL_BLK of each block as shown in FIG. 4B .
  • the representative value interpolating unit 111 B interpolates the APL APL_BLK of each block and converts the APL APL_BLK of each block into an APL APL_PIX of each pixel.
  • the luminance transfer curve generating unit 111 C generates a plurality of luminance transfer curves LTC 1 to LTCk previously determined based on the APLs. For example, as shown in FIG. 4D , the luminance transfer curve generating unit 111 C may generate five previously determined luminance transfer curves respectively corresponding to 0 APL, 64 APL, 128 APL, 192 APL, and 255 APL.
  • the luminance transfer curves LTC 1 to LTCk are set to have different slopes in a plane of input luminance Y-output luminance Y based on the corresponding APLs.
  • the luminance transfer curves LTC 1 to LTCk are set to have slopes capable of expanding a gray level distribution in a specific portion (for example, a portion with a gray level equal to or less than about 40% of a peak white gray level or a portion with a gray level equal to or greater than about 60% of the peak white gray level) of the input image.
  • the data modulating unit 111 D receives the APL APL_PIX of each pixel from the representative value interpolating unit 111 B and receives the luminance transfer curves LTC 1 to LTCk from the luminance transfer curve generating unit 111 C.
  • the data modulating unit 111 D selects a luminance transfer curve most suitable for each pixel based on the APL APL_PIX of each pixel. It is preferable that the number of luminance transfer curves is less than the number of APLs for a size reduction of hardware. Alternatively, as shown in FIG.
  • the data modulating unit 111 D may interpolates adjacent luminance transfer curves at opposite sides of the APL APL_PIX of each pixel to generate a luminance transfer curve corresponding to the APL APL_PIX of each pixel.
  • the data modulating unit 111 D maps the luminance components Y of the input digital video data RGB to the luminance transfer curve selected or generated for each pixel and performs a first modulation on the luminance components Y of the input digital video data RGB.
  • the data modulating unit 111 D then outputs first modulated luminance components Y′.
  • FIG. 4F illustrates an image whose the local contrast enhancement is performed through the first modulation. As shown in FIG.
  • a gray level distribution of each of a dark portion A 1 and a bright portion A 2 is expanded, and thus a loss of the detailed portion (i.e., the dark portion A 1 and the bright portion A 2 ) of the image are greatly reduced and prevented.
  • the global modulation circuit 112 receives the first modulated luminance components Y′ from the local modulation circuit 111 .
  • the global modulation circuit 112 performs a second modulation on the first modulated luminance components Y′ using various known methods and then outputs second modulated luminance components Y′′.
  • the entire contrast i.e., the global contrast of the image is improved through the second modulation.
  • the second modulated luminance components Y′′ are combined with color difference components U and V by a luminance/color difference component combining unit (not shown) included in the data modulation circuit 11 to generate the modulated digital video data R′G′B′.
  • FIG. 5 is an image of the result of an experiment illustrating a detailed enhancement effect when both the local contrast and the global contrast are enhanced as shown in FIG. 2 , compared with a detailed enhancement effect when only the global contrast is enhanced in the related art.
  • FIG. 5(C) is an image obtained when only the global contrast enhancement is performed in the same manner as the related art. As shown in FIG. 5(C) , a contrast ratio of the image according to the related art is greater than a contrast ratio of an original image illustrated in FIG. 5(A) . However, a detailed loss of a specific portion S of the related art image deepens because of the uniform contrast enhancement in the related art.
  • FIG. 5(B) is an image obtained when both the local contrast enhancement and the global contrast enhancement are performed in the same manner as the exemplary embodiment of the invention.
  • a contrast ratio of the image according to the exemplary embodiment of the invention is much greater than the contrast ratio of the original image illustrated in FIG. 5(A) , and a detailed loss scarcely exists in a specific portion S of the image.
  • the exemplary embodiment of the invention performs the local contrast enhancement prior to the global contrast enhancement, the exemplary embodiment of the invention previously expands a gray level distribution of a portion (for example, a very dark portion or a very bright portion) expected to generate the detailed loss of the image when the global contrast enhancement is performed, thereby minimizing the detailed loss of the image.
  • a portion for example, a very dark portion or a very bright portion
  • a halo is generated in a partial image, for example, in a boundary region between partial images (for example, a dark portion and a bright portion) having a high contrast ratio as shown in FIG. 6 .
  • the halo phenomenon is generated because all of boundary regions of a real image cannot be represented by a limited number of blocks. A method for solving such a defect is proposed below.
  • FIG. 7 illustrates another exemplary configuration of the data modulation circuit 11 .
  • the data modulation circuit 11 includes a local modulation circuit 211 for local contrast enhancement and a global modulation circuit 212 for global contrast enhancement.
  • the local modulation circuit 211 includes a first representative value calculating unit 211 A, a first representative value filtering unit 211 B, a first representative value interpolating unit 211 C, a luminance transfer curve generating unit 211 D, a second representative value calculating unit 211 E, and a data modulating unit 211 F.
  • the first representative value calculating unit 211 A receives the luminance components Y of the input digital video data RGB from the luminance/color difference component separating unit (not shown) included in the data modulation circuit 11 .
  • the first representative value calculating unit 211 A matches the luminance components Y of the input digital video data RGB to the plurality of virtual blocks B (0, 0) to B (n ⁇ 1, m ⁇ 1) obtained by dividing the display screen of the display panel 10 in the matrix form as shown in FIG. 3 to calculate a first representative value of each of the virtual blocks B (0, 0) to B (n ⁇ 1, m ⁇ 1).
  • the first representative value of each block may be implemented by an APL of each block.
  • the first representative value calculating unit 211 A obtains a maximum gray level of each pixel in each block and divides a sum of the maximum gray levels of the pixels included in each block by the total number of pixels of each block, so as to calculate an APL APL_BLK of each block.
  • the first representative value filtering unit 211 B receives the APL APL_BLK of each block from the first representative value calculating unit 211 A and filters the APL APL_BLK of each block using a low pass filter with j ⁇ j size shown in FIG. 8 , where j is 3, for example. Hence, a halo generation in a boundary region between the adjacent blocks is prevented.
  • C (y, x) indicates a coefficient of the low pass filter, and a weight value of C (1, 1) is set to be greater than weight values of other coefficients having the same value.
  • the first representative value filtering unit 211 B may filter the APL APL_BLK of each block through the following Equation 1.
  • the APL APL_BLK of each block is converted into a filtered APL APL′_BLK of each block by the filtering process using the low pass filter.
  • the first representative value interpolating unit 211 C interpolates the filtered APL APL′_BLK of each block and converts the filtered APL APL′_BLK of each block into an APL APL_PIX of each pixel.
  • the luminance transfer curve generating unit 211 D generates a plurality of luminance transfer curves LTC 1 to LTCk previously determined based on the APLs.
  • the luminance transfer curve generating unit 211 D may generate five previously determined luminance transfer curves respectively corresponding to 0 APL, 64 APL, 128 APL, 192 APL, and 255 APL.
  • the luminance transfer curves LTC 1 to LTCk are set to have different slopes in a plane of input luminance Y-output luminance Y based on the corresponding APLs.
  • the second representative value calculating unit 211 E analyzes the luminance components Y of the input digital video data RGB to calculate a second representative value.
  • the second representative value may be implemented by a global APL APL_GBL representing the entire image.
  • the data modulating unit 211 F receives the APL APL_PIX of each pixel from the first representative value interpolating unit 211 C and receives the luminance transfer curves LTC 1 to LTCk from the luminance transfer curve generating unit 211 D.
  • the data modulating unit 211 F selects a luminance transfer curve most suitable for each pixel based on the APL APL_PIX of each pixel. It is preferable that the number of luminance transfer curves is less than the number of APLs for a size reduction of algorithm.
  • the data modulating unit 211 F may interpolate adjacent luminance transfer curves at opposite sides of the APL APL_PIX of each pixel to generate a luminance transfer curve corresponding to the APL APL_PIX of each pixel.
  • the data modulating unit 211 F adjusts a slope of the luminance transfer curve selected or generated for each pixel based on the global APL APL_GBL received from the second representative value calculating unit 211 E as indicated by the following Equation 2, thereby previously preventing an excessive expansion of a gray level distribution.
  • Y ′′ ( Y ′ ⁇ )+( Y ⁇ (1 ⁇ )), 0 ⁇ 1 [Equation 2]
  • Equation 2 Y′′ is a luminance value by the luminance transfer curve after the slope of the luminance transfer curve of each pixel is adjusted, Y′ is a luminance value by the luminance transfer curve before the slope of the luminance transfer curve of each pixel is adjusted, and a is a function value of the global APL APL_GBL.
  • the data modulating unit 211 F maps the luminance components Y of the input digital video data RGB to the luminance transfer curve having the adjusted slope and performs a first modulation on the luminance components Y of the input digital video data RGB.
  • the data modulating unit 211 F then outputs first modulated luminance components Y′′.
  • the global modulation circuit 212 receives the first modulated luminance components Y′′ from the local modulation circuit 211 .
  • the global modulation circuit 212 performs a second modulation on the first modulated luminance components Y′′ using various known methods and then outputs second modulated luminance components Y′′′.
  • the entire contrast i.e., the global contrast of the image is improved through the second modulation.
  • the second modulated luminance components Y′′′ are combined with color difference components U and V by the luminance/color difference component combining unit (not shown) included in the data modulation circuit 11 to generate the modulated digital video data R′G′B′.
  • the display device and the contrast enhancement method thereof divide the image into the plurality of blocks and individually apply the luminance transfer curve of each block, thereby minimizing the detailed loss of the image and improving the contrast characteristic.
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